The background description provided herein is for the purpose of generally presenting the context of the invention. The subject matter discussed in the background of the invention section should not be assumed to be prior art merely as a result of its mention in the background of the invention section. Similarly, a problem mentioned in the background of the invention section or associated with the subject matter of the background of the invention section should not be assumed to have been previously recognized in the prior art. The subject matter in the background of the invention section merely represents different approaches, which in and of themselves may also be inventions. Work of the presently named inventors, to the extent it is described in the background of the invention section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the invention.
Lubrication reduces the friction between contacting surfaces and thus increases the energy efficiency of engines and other machines. It can also reduce the degree of wear damage, which increases the life time of the interactive components and prevents catastrophic buildup of wear debris. Many types of nanoparticles have been studied as lubricant additives [1,2], because they offer the ability to enter the contact area between sliding surfaces and protect them from directly rubbing against each other, an ability that small molecular additives lack [2-4]. This makes nanoparticles effective for reducing the so called boundary friction, such as that during the startup of an engine, when the surfaces tend to closely contact each other at a relatively low speed and inflict their most significant wear damage [2-4]. Under such severe friction conditions, the lubricant additives in the contact areas are subject to high local mechanical stresses and sometimes, high temperatures, which can cause molecular modifiers to rub off, decompose, or simply fail to provide a sufficiently thick coverage between the roughened mating surfaces[2-4]. Therefore, nanoparticles are appealing by virtue of their size and their chemical and thermal stability under tribological conditions. However, it is challenging to disperse nanoparticles in lubricating oils. Typically this requires surface functionalization with surfactant-like substances, which themselves are prone to degradation under tribological conditions, leading to unstable lubrication properties for the nanoparticles [2]. Ideally, high performance nanoparticle additives should be able to sustain the chemical and mechanical stresses while remaining dispersed in the lubricant oil.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.